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Message-ID: <20210618135158.GB81946@suse.de>
Date: Fri, 18 Jun 2021 15:51:58 +0200
From: Mian Yousaf Kaukab <ykaukab@...e.de>
To: Mikko Perttunen <cyndis@...si.fi>
Cc: Mikko Perttunen <mperttunen@...dia.com>, arnd@...db.de,
gregkh@...uxfoundation.org, linux-tegra@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] misc: sram: Only map reserved areas in Tegra SYSRAM
On Fri, Jun 18, 2021 at 12:26:21PM +0300, Mikko Perttunen wrote:
> On 6/18/21 11:18 AM, Mian Yousaf Kaukab wrote:
> > On Thu, Jun 17, 2021 at 12:48:04PM +0300, Mikko Perttunen wrote:
> > > On Tegra186 and later, a portion of the SYSRAM may be reserved for use
> > > by TZ. Non-TZ memory accesses to this portion, including speculative
> > > accesses, trigger SErrors that bring down the system. This does also
> > > happen in practice occasionally (due to speculative accesses).
> > >
> > > To fix the issue, add a flag to the SRAM driver to only map the
> > > device tree-specified reserved areas depending on a flag set
> > > based on the compatibility string. This would not affect non-Tegra
> > > systems that rely on the entire thing being memory mapped.
> > >
> > > Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
> > > ---
> > > drivers/misc/sram.c | 108 +++++++++++++++++++++++++++++++-------------
> > > drivers/misc/sram.h | 9 ++++
> > > 2 files changed, 86 insertions(+), 31 deletions(-)
> > >
> > > diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
> > > index 93638ae2753a..a27ffb3dbea8 100644
> > > --- a/drivers/misc/sram.c
> > > +++ b/drivers/misc/sram.c
> > > @@ -97,7 +97,24 @@ static int sram_add_partition(struct sram_dev *sram, struct sram_reserve *block,
> > > struct sram_partition *part = &sram->partition[sram->partitions];
> > > mutex_init(&part->lock);
> > > - part->base = sram->virt_base + block->start;
> > > +
> > > + if (sram->config->map_only_reserved) {
> > > + void *virt_base;
> > > +
> > > + if (sram->no_memory_wc)
> > > + virt_base = devm_ioremap_resource(sram->dev, &block->res);
> > > + else
> > > + virt_base = devm_ioremap_resource_wc(sram->dev, &block->res);
> > > +
> > > + if (IS_ERR(virt_base)) {
> > > + dev_err(sram->dev, "could not map SRAM at %pr\n", &block->res);
> > > + return PTR_ERR(virt_base);
> > > + }
> > > +
> > > + part->base = virt_base;
> > > + } else {
> > > + part->base = sram->virt_base + block->start;
> > > + }
> > > if (block->pool) {
> > > ret = sram_add_pool(sram, block, start, part);
> > > @@ -198,6 +215,7 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
> > > block->start = child_res.start - res->start;
> > > block->size = resource_size(&child_res);
> > > + block->res = child_res;
> > > list_add_tail(&block->list, &reserve_list);
> > > if (of_find_property(child, "export", NULL))
> > > @@ -295,15 +313,17 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
> > > */
> > > cur_size = block->start - cur_start;
> > > - dev_dbg(sram->dev, "adding chunk 0x%lx-0x%lx\n",
> > > - cur_start, cur_start + cur_size);
> > > + if (sram->pool) {
> > > + dev_dbg(sram->dev, "adding chunk 0x%lx-0x%lx\n",
> > > + cur_start, cur_start + cur_size);
> > > - ret = gen_pool_add_virt(sram->pool,
> > > - (unsigned long)sram->virt_base + cur_start,
> > > - res->start + cur_start, cur_size, -1);
> > > - if (ret < 0) {
> > > - sram_free_partitions(sram);
> > > - goto err_chunks;
> > > + ret = gen_pool_add_virt(sram->pool,
> > > + (unsigned long)sram->virt_base + cur_start,
> > > + res->start + cur_start, cur_size, -1);
> > > + if (ret < 0) {
> > > + sram_free_partitions(sram);
> > > + goto err_chunks;
> > > + }
> > > }
> > > /* next allocation after this reserved block */
> > > @@ -331,40 +351,66 @@ static int atmel_securam_wait(void)
> > > 10000, 500000);
> > > }
> > > +static const struct sram_config default_config = {
> > > +};
> > > +
> > > +static const struct sram_config atmel_securam_config = {
> > > + .init = atmel_securam_wait
> > > +};
> > > +
> > > +/*
> > > + * SYSRAM contains areas that are not accessible by the
> > > + * kernel, such as the first 256K that is reserved for TZ.
> > > + * Accesses to those areas (including speculative accesses)
> > > + * trigger SErrors. As such we must map only the areas of
> > > + * SYSRAM specified in the device tree.
> > > + */
> > > +static const struct sram_config tegra_sysram_config = {
> > > + .map_only_reserved = true,
> >
> > In case of Tegra sram base is 64K aligned and the reserved partitions
> > are 4K aligned. How this flag will work if the kernel is using 64K
> > page size?
>
> Good point - perhaps we need to consider another approach that just excludes
> any inaccessible areas, though I think it'll be somewhat more complicated
> and more Tegra-specific.
Perhaps SError due to speculative access can be avoided by just using
no-memory-wc, provided the performance impact due to this is OK for
bpmp driver.
>
> I'm going on vacation starting this evening so I'll look into this
> afterwards.
Enjoy your vacations!
>
> Thanks,
> Mikko
BR,
Yousaf
>
> >
> > > +};
> > > +
> > > static const struct of_device_id sram_dt_ids[] = {
> > > - { .compatible = "mmio-sram" },
> > > - { .compatible = "atmel,sama5d2-securam", .data = atmel_securam_wait },
> > > + { .compatible = "mmio-sram", .data = &default_config },
> > > + { .compatible = "atmel,sama5d2-securam", .data = &atmel_securam_config },
> > > + { .compatible = "nvidia,tegra186-sysram", .data = &tegra_sysram_config },
> > > + { .compatible = "nvidia,tegra194-sysram", .data = &tegra_sysram_config },
> > > {}
> > > };
> > > static int sram_probe(struct platform_device *pdev)
> > > {
> > > + const struct sram_config *config;
> > > struct sram_dev *sram;
> > > int ret;
> > > struct resource *res;
> > > - int (*init_func)(void);
> > > +
> > > + config = of_device_get_match_data(&pdev->dev);
> > > sram = devm_kzalloc(&pdev->dev, sizeof(*sram), GFP_KERNEL);
> > > if (!sram)
> > > return -ENOMEM;
> > > sram->dev = &pdev->dev;
> > > + sram->no_memory_wc = of_property_read_bool(pdev->dev.of_node, "no-memory-wc");
> > > + sram->config = config;
> > > +
> > > + if (!config->map_only_reserved) {
> > > + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > + if (sram->no_memory_wc)
> > > + sram->virt_base = devm_ioremap_resource(&pdev->dev, res);
> > > + else
> > > + sram->virt_base = devm_ioremap_resource_wc(&pdev->dev, res);
> > > + if (IS_ERR(sram->virt_base)) {
> > > + dev_err(&pdev->dev, "could not map SRAM registers\n");
> > > + return PTR_ERR(sram->virt_base);
> > > + }
> > > - res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > - if (of_property_read_bool(pdev->dev.of_node, "no-memory-wc"))
> > > - sram->virt_base = devm_ioremap_resource(&pdev->dev, res);
> > > - else
> > > - sram->virt_base = devm_ioremap_resource_wc(&pdev->dev, res);
> > > - if (IS_ERR(sram->virt_base)) {
> > > - dev_err(&pdev->dev, "could not map SRAM registers\n");
> > > - return PTR_ERR(sram->virt_base);
> > > + sram->pool = devm_gen_pool_create(sram->dev, ilog2(SRAM_GRANULARITY),
> > > + NUMA_NO_NODE, NULL);
> > > + if (IS_ERR(sram->pool))
> > > + return PTR_ERR(sram->pool);
> > > }
> > > - sram->pool = devm_gen_pool_create(sram->dev, ilog2(SRAM_GRANULARITY),
> > > - NUMA_NO_NODE, NULL);
> > > - if (IS_ERR(sram->pool))
> > > - return PTR_ERR(sram->pool);
> > > -
> > > sram->clk = devm_clk_get(sram->dev, NULL);
> > > if (IS_ERR(sram->clk))
> > > sram->clk = NULL;
> > > @@ -378,15 +424,15 @@ static int sram_probe(struct platform_device *pdev)
> > > platform_set_drvdata(pdev, sram);
> > > - init_func = of_device_get_match_data(&pdev->dev);
> > > - if (init_func) {
> > > - ret = init_func();
> > > + if (config->init) {
> > > + ret = config->init();
> > > if (ret)
> > > goto err_free_partitions;
> > > }
> > > - dev_dbg(sram->dev, "SRAM pool: %zu KiB @ 0x%p\n",
> > > - gen_pool_size(sram->pool) / 1024, sram->virt_base);
> > > + if (sram->pool)
> > > + dev_dbg(sram->dev, "SRAM pool: %zu KiB @ 0x%p\n",
> > > + gen_pool_size(sram->pool) / 1024, sram->virt_base);
> > > return 0;
> > > @@ -405,7 +451,7 @@ static int sram_remove(struct platform_device *pdev)
> > > sram_free_partitions(sram);
> > > - if (gen_pool_avail(sram->pool) < gen_pool_size(sram->pool))
> > > + if (sram->pool && gen_pool_avail(sram->pool) < gen_pool_size(sram->pool))
> > > dev_err(sram->dev, "removed while SRAM allocated\n");
> > > if (sram->clk)
> > > diff --git a/drivers/misc/sram.h b/drivers/misc/sram.h
> > > index 9c1d21ff7347..d2058d8c8f1d 100644
> > > --- a/drivers/misc/sram.h
> > > +++ b/drivers/misc/sram.h
> > > @@ -5,6 +5,11 @@
> > > #ifndef __SRAM_H
> > > #define __SRAM_H
> > > +struct sram_config {
> > > + int (*init)(void);
> > > + bool map_only_reserved;
> > > +};
> > > +
> > > struct sram_partition {
> > > void __iomem *base;
> > > @@ -15,8 +20,11 @@ struct sram_partition {
> > > };
> > > struct sram_dev {
> > > + const struct sram_config *config;
> > > +
> > > struct device *dev;
> > > void __iomem *virt_base;
> > > + bool no_memory_wc;
> > > struct gen_pool *pool;
> > > struct clk *clk;
> > > @@ -29,6 +37,7 @@ struct sram_reserve {
> > > struct list_head list;
> > > u32 start;
> > > u32 size;
> > > + struct resource res;
> > > bool export;
> > > bool pool;
> > > bool protect_exec;
> > > --
> > > 2.30.1
> >
> > BR,
> > Yousaf
> >
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